A one-way clutch is also used for preventing reverse rotation of rollers of a sloping conveyor, a bucket elevator, etc., and is often used in the environment exposed to particles. Since there is a risk of causing problems such as operation failure of the cam due to the foreign matters that enter inside the one-way clutch, the one-way clutch that has the dustproof function has been developed.
In addition, when the one-way clutch is used for preventing a reverse running of a conveyor etc., the inner race is connected to a rotary shaft and the outer race is prevented from rotating relative to the inner race. And the one-way clutch is configured so that the inner race is in the idle mode when the rotary shaft rotates in the normal direction, and the rotation of the rotary shaft is stopped by engaging the cams with the inner race and the outer race in case the rotary shaft rotates in the reverse direction. When the inner race is in the idle mode, the inner race may be shifted to any direction relative to the outer race due to the vibration of itself and the like. Therefore, a structure for a dustproof function requires allowing the mutual deviation in any direction of the inner race and the outer race. The following are examples of the one-way clutch having such a dustproof function:
Patent document 1 Japanese Unexamined Patent Application Publication No. 1979-36441
Patent document 2 Japanese Unexamined Patent Application Publication No. 1977-156263
A one-way clutch having cams (sprags) between an inner race and an outer race, seal supporters fixed to axial direction outer sides of the outer race than the cams, and oil seals attached to the seal supporters wherein lips of the oil seals contact with the outer circumferential surface of the inner race is disclosed in the patent document 1.
A one-way clutch in patent document 2, as in the case of the patent document 1, has cams (sprags) between an inner race and an outer race, seal supporters fixed to an axial direction outer sides of the outer race than the cams, and oil seals attached to the seal supporters wherein lips of the oil seals contact with the outer circumferential surface of the inner race. Furthermore, the one-way clutch has grease seal members which are attached to the axial direction outer sides of the outer race than the oil seals and have recesses facing the outer circumferential surface of the inner race. The dustproof function can be realized by filling the grease into the recesses of the grease seal members.
When the lips of the oil seals contact with the outer circumferential surface of the inner race of the one-way clutch as described in patent documents 1 and 2, it is sometimes required to replace the oil seals, because the lips contacting with the outer circumferential surface of the inner race wear due to adhesion of particles so that the dustproof function may decrease.
In order to solve the above-mentioned problem, it is also considered that two oil seals are provided in the axial direction so as to prevent particles from entering inside the clutch by the oil seal located outside in the axial direction. In this case, however, not only the axial dimension of the one-way clutch should be large, but also the manufacturing cost may be increased. In addition, there is also a problem that the working conditions of the one-way clutch are restricted by heat generation due to the friction between the oil seal and the inner race.
On the other hand, when additional grease seal members are provided in the one-way clutch as described in the patent document 2, it is temporarily possible to prevent particles from entering the one-way clutch by the grease filled inside the grease seal members. Therefore, the adhesion of particles on the lips of the oil seal can be prevented and the dustproof performance can be enhanced. In order to maintain the dustproof performance, however, it is required that the grease is filled and replaced regularly since the grease is contaminated by the particles and flowing out with time. Therefore, the maintenance is not easy.